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The work investigates the effect of different Iron and Manganese contents in ad-hoc cast specimens made from recycled EN AC-43200 alloy. Tensile tests and metallographic analyses coupled with energy dispersive X-ray spectroscopy measurements are carried out to elucidate the interplay between the microstructure and the quasi-static properties of the Aluminium-Silicon alloy under investigation. A strong correlation between the composition and morphology of Fe/Mn -based intermetallic precipitates and tensile properties is demonstrated. Moreover, it is found that specific intermetallic phases are present only for certain, relative and/or absolute contents of Fe and Mn.

In recent years, brakes emission tests have become increasingly standardized to meet progressively stricter intra and inter laboratory reproducibility requirements. In particular, following the recent EURO 7 regulation proposal, WLTP-Brake cycle has surged as EU standard braking sequence to determine emission factors of investigated brake systems. Furthermore, the UN GTR (United Nations Global Technical Regulation) on Laboratory Measurement of Brake Emissions for Light-Duty Vehicles collects all the information needed to perform emission tests in laboratory. This includes design specifications for the testing platforms as well as the typology and configuration of measuring instruments.

The manuscript proposes a fundamental investigation regarding the corrosion resistance of anodized EN-AC-42200 Aluminum alloy specimens, showing different microstructures. In particular, the microstructures are analyzed in terms of secondary dendrite arm spacing (SDAS), while the corrosion resistance of anodized samples is evaluated by using electrochemical noise measurements (ENM) and associated Noise Resistance (Rn) values. Specimens with five different SDAS values are considered in order to discuss the interplay among: a) microstructure of the alloy; b) anodic layer morphology; and c) corrosion protection of the anodic layer. An inverse proportionality between SDAS value and corrosion resistance is demonstrated.

nPETS - nanoParticle Emissions from the Transport Sector - is an EU- funded project within the Horizon 2020 research and innovation program, with the aim of characterizing specifically the emission amount, the chemical composition and the toxicological behavior of nano-particulates produced by different exhaust and non-exhaust emission sources related to the transport sector. Started in June 2021, its final goal is to provide a wide scientific background for informed public health policies aiming to tackle transport-related nano-particulates, while developing sound technologies for their collection, chemical analysis and toxicological characterization. In particular, the chemical characterization of the collected nano-particulates is of fundamental importance in determining the presence of univocal markers for specific emission sources in different environments.

The reliable chemical characterization of non-exhaust emissions generated by brakes is of fundamental importance in order to provide correct information for source apportionment studies as well as for their toxicological and environmental assessment. Nowadays, the best option to obtain samples of PM10 emissions composed only by material worn from the tribological interface, i.e. the braking disc (BD) and the friction material (FM) rubbing surfaces, is to sample them on suitable collection filters at a dedicated dyno-bench, during a standard braking test cycle. In particular, the use of enclosed dyno-bench is necessary for excluding other spurious contributions from the environment, while defined test cycles are necessary to simulate standard driving conditions.

The work investigates the use of cathodic protection -based strategies (e.g. sacrificial anodes) with the aim of extending the corrosion resistance of Aluminum components to be used in disc brake systems. Lab-scale electrochemical measurements, including voltammetry and zero resistance ammetry (ZRA), are used to: a) define the requirements of a cathodic protection system for a 42200 Aluminum alloy; b) evaluate the protection capability of a Zn-based sacrificial anode; and c) demonstrate an extended corrosion resistance of the protected part even in the presence of a galvanic coupling, with respect to the unprotected condition.

The manuscript reports about the corrosion performance of a series of grey cast iron specimens including an increasing concentration of Aluminum as alloying element. An improved corrosion resistance for %Al >1%wt is demonstrated and a reasonable corrosion mechanism is proposed as well. Electrochemical techniques allow to calculate a particularly high corrosion potential (Ecorr) for the sample including 4%wt Al, equals to -572 mV vs. Saturated Calomel Electrode (SCE). The manuscript is aimed at demonstrating that the fine tuning of alloying elements in cast iron is a particularly effective method in order to improve its corrosion resistance, thus allowing the development of future disc-brake rotors with a prolonged operating life.

Brake calipers for high-end cars are typically realized using Aluminum alloys, with Silicon as the most common alloying element. Despite the excellent castability and machinability of Aluminum-Silicon alloys (AlSix), anodization is often required in order to increase its corrosion resistance. This is particularly true in Chlorides-rich environments where Aluminum can easily corrode. Even if anodization process is known for almost 100 years, anodization of AlSix -based materials is particularly challenging due to the presence of eutectic Silicon precipitates. These show a poor electric conductivity and a slow oxidation kinetics, leading to inhomogeneous anodic layers. Continuous research and process optimization are required in order to develop anodic layers with enhanced morphological and electrochemical properties, targeting a prolonged resistance of brake calipers under endurance corrosive tests (e.g. >1000 hours Neutral Salt Spray (NSS) tests).

The manuscript firstly overviews the corrosion potentials of several components used in disk-brake systems. Particular attention is devoted to the couplings between materials with different nobility. It is demonstrated that if two materials: a) show a difference in their corrosions potential (Ecorr) >100mV; and b) are in electric contact in the presence of an electrolyte; they can form a galvanic couple (GC) which could undergo severe corrosive phenomena. In the second part, the paper focuses on the anodized Aluminium (ANOD-Al)-stainless steel (SS) GC. This couple is investigated since: 1) anodized Al and SS are often comprised in high-end braking systems and typically constitute the caliper body (anodized Al) and several components (springs, pins, screws, metal plates, rods, shims etc.) included; and 2) it shows one of the largest corrosion potential difference among all materials included in a braking system (>500mV).

Brake pads employing innovative hydraulic inorganic binders in place of common state-of-the-art thermosetting phenolic resins have been produced by means of a unique prototypal equipment and a distinctive manufacturing process. The unicity of the process enables us to exclude completely any thermal cycle in the manufacturing steps, with a considerable positive energy balance compared to the standard counterpart. Realized brake pads have indeed been successfully tuned to meet the braking performances of phenolic counterparts. In the present work our latest efforts in this field are illustrated, focusing our attention to three main areas of interest: performance, energy consumption, volatile organic emissions.

Organic brake pads for automotive can be defined as brake linings with bonding matrix constituted of high-temperature thermosetting resins. Bonded together inside the polymeric binder are a mix of components (e.g. abrasives, lubricants, reinforcements, fillers, modifiers…), each playing a distinctive role in determining the tribology and friction activity of the final friction material. The herein reported work presents inorganic “alkali-activated”-based materials suitable for the production of alternative brake linings (i.e. brake pads), by means of an unconventional low-temperature wet process. Exploiting the hydraulic activity of specific components when exposed to an alkaline environment, such peculiar inorganic materials are capable of coming to a complete hardening without the need of traditional high-temperature energivorous procedures.